During Leg 185, five whole-round samples and eight pieces of representative sediments and rocks from Site 1149 were taken and immediately sealed in bags for subsequent shore-based permeability experiments. Rock pieces were cut into a cylindrical shape for the measurement. Images of the samples are shown in Figure F1. Using the fragments of sediments and rocks, wet bulk density, porosity, void ratio, water content, and electrical resistivity were measured (Table T1).
Before the permeability testing, the samples should be consolidated under the estimated in situ confining pressure. The estimation is based on the following equation:
Because clayey samples often show intense dilatancy after coring, it is necessary to perform a consolidation test under the estimated confining pressure. The pressures are 0.74 kgf/cm2 for Section 185-1149A-3H-4; 2.72 kgf/cm2 for Section 8H-4; 4.54 kgf/cm2 for Section 13H-4; 5.80 kgf/cm2 for Section 17H-2; and 6.56 kgf/cm2 for Section 3R-1. Hard rocks have slight dilatancy, so the confining pressure of 5.00 kgf/cm2 was used for all the rocks. The triaxial compressive machine was used for testing the samples (Fig. F2). The consolidated volumes are plotted with time (Fig. F3). The volume of clayey samples decreases with time, and pelagic clays show secondary consolidation that may result from rearrangement of clay minerals. After this testing, permeabilities were measured under the confined pressure and room temperature (20°C). The experiments were conducted by the steady-state method, which entails measurement of volumetric flow-through rate under a constant fluid pressure gradient. The measurements have good linearities between the volume of outflow and time. Measured permeabilities are shown in Table T1.